How to determine enclosure frequency

[CrownVic 15]

I have a 15" sub in a box that is 4 cubes before port and sub. The box has 2 32" ports. I tried google and the search function on here but i couldn't find a way to figure out the tuning frequency of the box.

Thanks for the help If any more information is needed please let me know.

[killa101 0]

I have a 15" sub in a box that is 4 cubes before port and sub. The box has 2 32" ports. I tried google and the search function on here but i couldn't find a way to figure out the tuning frequency of the box.

Thanks for the help If any more information is needed please let me know.

To determine the tuning frequency you need the internal volume of the enclosure, the length of the port(s), and the cross sectional area of the ports.

Did you mean your enclosure has two 3" round ports or two 32" long port? If it is a 3" round port then we need the length of the port and if it is the 32" port we need the port width and depth.

You can use this calculator to determine the tuning once these things are known. Otherwise you can post the info here and we can try to determine it.

[ppiflat10s 3]

I always use winisd, start a project and then enter in the volume of my box, enter the number of ports and port area, and then keep adjusting the tuning freq. til the port length it gives you matches the length of the port in the box.

[CrownVic 15]

It has two ports with thirty-two inches of port area for 64 inches of total port area. I have to measure the lenght today.

[jcarter1885 995]

It has two ports with thirty-two inches of port area for 64 inches of total port area. I have to measure the lenght today.

Give us way more information than you are now, like box size outside(height x width x length) and both port dimensions(height x width x length) not just the square area of the port.

[CrownVic 15]

Im gonna measure it tomorrow when i get out of school tomorrow its dark now.

So you need length width depth and height? How do i measure the port length?

Once again thanks for the help.

[KU40 173]

Measure down the center of the port. If the port turns, measure to the center of the turn, then turn and go down the center of the last bit of port.

[CrownVic 15]

This is a picture i tried to draw in paint but for some reason it came out small.

The inside dememsions are

Depth 16"

Width 21"

Height 20"

I dont know if i measured the port length right or not but i showed how i got it in the pic. Its 12"

The box is 3.9 cubes

[shizzzon 461]

i have a question-

how are you getting 16x2" ports if the internal height is 20"?

Do they actually only go up 16" or did u make a mistake?

[shizzzon 461]

i'll go ahead and say if that's true.. u have 2 16x2" ports 12" long per port... then u are tuned to 57hz which is STUPID if this is intended for music.

Your measurements or our info may be off but if it isnt... that's what it is.

Again, if it's really tuned that high, you are missing out...

[ppiflat10s 3]

maybe he mislabeld the height/width/depth. because one measurement he gave was 16", so maybe his height was 16, width is 21, depth is 20. although that puts it way out of scale in the drawing because if it was 20 deep, that 12" port is way to long compared to the 8" behind it. but the 2" wide ports arent close to scale in regards to a 21" width, so it could be 16 tall and 20 deep.

I plugged it all into winisd and assuming 3/4" port walls, and your 12" port is measured from the face of the box and only extends into the box 11.25" as well as the port being 16 and the height being 16. then I got 3.316 ft^3 tuned at 52.35

if you took one of the ports and broke out the inner port wall, and cut a little 2"x16" peice of mdf and glue it in to seal off one port, then the box becomes 3.6ft^3 tuned to 35.5, but then youre quite a bit short on port area as it will be 24 in^2 where it should be anywhere between 43 and 58 in^2. you might end up with port noise, but if you got lucky and didnt, this box would at least sound alot better than in its current configuration. it could get you by while you wait to buy/build a new box.

Edited October 8, 2009 by ppiflat10s

[CrownVic 15]

Well the 57hz tuning would explain while its so much louder on higher bass frequencys. I guess i messed up when designing it. And the demensions are all after i subtracted 1.5" for the Material.

Its a real shame i phucked up the box design because its a super nice box. Heres a pic.

[CrownVic 15]

Would i be able to Take off the ports and go with a new port design? Like replacing only the wall the sub mounts in and taking out the old ones. Would i notice more output at lower frequencies if the box was tuned to around say 35hz?

thanks for the info.

[CrownVic 15]

Any thoughts on this?

[wof131s 10]

If it were me, i would do just that. Replace the wall that the sub is mounted on, remove both ports (35Hz is just a lil bit high for my taste) and create a new front end for the sub to be mounted to. Use 12-16^2 inch of port per cubic feet of airspace, create a nice big port (not to big though, or it will sound like sh$t) and see how it sounds. remeber to calculate the size of your port so that you would have the recommended airspace need to get the most out of your sub. Or if you dont want to do that just build a new box, but make sure you get the right info this time. Good Luck.

Edited October 15, 2009 by wof131s

[CrownVic 15]

ok thanks. For the time being it doesnt matter anyways because my alternator fried.

[CrownVic 15]

Well im going to build a new box thursday.

Could somone here please help me with a design.

I just want something simple atleast 4 cubes net, and tuned to 33hz instead of the ridiculous 53hz its tuned to now. I was also wondering if i would notice any more lower end output and I wanted to make sure its worth the trouble to rebuild a box.

I didn't want to clutter the boards thats why i didn't start a new topic. But thanks for your time and if you need anymore info just let me know.

[KU40 173]

Oh my goodness it will be a complete night and day difference on the low end with the new box. If you give us some maximum dimensions you want the box to be we can whip something up right quick.

[CrownVic 15]

ok thanks alot.

Here are the dimensions of the old box

The inside dememsions are

Depth 16"

Width 21"

Height 20"

The box is 3.9 cubes

It can be a up to like 4 inches wider and my be 2 inches taller I wanna keep the same depth.

its going in the trunk of a crown vic.

Thanks again.

[KU40 173]

OK well if you make a box 16" deep x 25" wide x 22" tall you'll have 4.04 cubes gross. BTW, when you say enclosure volume, don't include the port and sub displacement. So your box isn't really 3.9 cubes. It's 3.9 minus sub and port displacement. That's the net volume and what you should use as actual enclosure volume for the sub.

Anyways, if you use three 4" PVC ports and make each 25" long you'll have a box that's about 3.35 cubes net tuned to 35 hz. I would have liked to say use two 4" aeroports to save some volume since you're a bit on the small side, but they would need to be 16" long and with your box depth only 16" deep you'd have to put in a 90" bend and I don't think aeroports fit well with regular 4" PVC 90* bends. But if somebody that has done it before can say that they do fit in regular PVC bends, I'd suggest the aeroports. Obviously with the three 4" PVC tubes I mentioned first, regular PVC bend pieces will fit correctly.

[CrownVic 15]

Well i was planning on making it bigger because if i remember right nick at IA told me it should be around 4 cubes optimal. Is there an advantage of using aero ports? A slot port would be easier.

the dimensions i listed were after subtracting the material.

If i change the interior dimensions to 17"x23"x20" that makes the total inner volume 4.5 cubes. Would that leave me enough room to give it the proper port to tune it any where from 32-36hz?

I have enough room to go an inch or two bigger on the height or width if need be?

[thebiggmann12 14]

sri to thread-jack but ku40, how do u find out what kinda pvc ports to run? i gotta small car and wanna build a box that is 35" wide 22" tall and 20" deep. i beleive that it come out to be 7.343 cubes, not including the 18" fi q and the ports...what would i need for the pvc ports to tune it to about 28 hz? also, would just using pvc from ur local menards work?

[thebiggmann12 14]

Well i was planning on making it bigger because if i remember right nick at IA told me it should be around 4 cubes optimal. Is there an advantage of using aero ports? A slot port would be easier.

the dimensions i listed were after subtracting the material.

If i change the interior dimensions to 17"x23"x20" that makes the total inner volume 4.5 cubes. Would that leave me enough room to give it the proper port to tune it any where from 32-36hz?

I have enough room to go an inch or two bigger on the height or width if need be?

the advantage to using aero ports is it doesnt take up as much space inside the box, so u basically have a bigger box on the inside, n get the same port area and tuning frequency.

[CrownVic 15]

Ok thanks.

I just don't know if ill have access to a router to make circle cuts. thats why i was going to use a slot port.

I just have to figure out how to determine the size of a port.

[thebiggmann12 14]

check out the re calculator...it lets u punch in basically everything u want and then gives u cut outs...i built my box like that and it came out great.